Saturable magnetic device



Jan. 5, 965 R. E. BOYLAN ETAL 3,164,811,

SATURABLE MAGNETIC DEVICE Filed Feb. 24. 1960 INVENTORS ROBERT E. BOYLANRICHARD J. PETSCHAUER United States Patent 3,164,811 SATURABLE MAGNETHCBEVECE Robert E. Boylan, St. Paul, and Richard I. Fetscha ier,Minneapolis, Minn, assignors to Sperry Rand Corporation, New York, N.Y.,a corporation of Delaware Filed Feb. 24, 1960, Ser. No. 10,679 5 Claims.(Cl. 340-174) This invention pertains to magnetic devices andparticularly such devices wherein transformation properties are relatedto conditions of magnetic saturation of a saturable element.

In many cases it is desired to have a maximum output operating with acore element unsaturated, but with a very minimum of output with thecore element substantially saturated. However, in the past the couplingof input or drive windings to output windings irrespective of coreaction has given rise to undesired outputs with saturation conditions inthe core. The present invention overcomes such disadvantages.

Briefly stated, in accordance with the present invention the input ordrive (hereinafter drive) winding is in two distributed portions, andthese wound oppositely. The output winding is positioned more intimatelywith the first portion of the drive winding than the remaining portion.The effective number of turns of the first portion of the drive windingis less than the effective turns of the remaining portion. The netresult is that during saturation, the close coupling of the firstportion of the drive winding, and the more remote coupling of theoppositely poled remaining portion thereof to the output winding, causea nullification in effect upon the output winding. However, duringnon-saturation, the aforesaid remaining portion of the drive winding,with its larger number of turns, is more closely coupled, by virtue ofthe element, to the output winding, and the result is an appreciableinduction in the output winding.

It is thus a principal object of the invention to provide for a maximumratio of output to input with a core element unsaturated, but a minimumsuch ratio with the element saturated. Further objects of the inventionand the entire scope thereof will become more fully apparent from thefollowing detailed description of an illustrative embodiment, and fromthe appended claims. The illustrative embodiment may be best understoodby reference to the accompanying drawings, wherein:

FIGURE 1 illustrates the embodiment of this invention showing asaturable magnetic element and the various windings associatedtherewith; and

FIGURE 1A illustrates the hysteresis characteristics of the magneticelement of FIGURE 1.

While the above illustrative embodiment involves the element in the formof a toroidal core, and used as a coincident current switch, clearly nolimitation thereto is necessary or intended. The invention is applicableto auysituation where an element may be operated at times in saturatedcondition, and at other times less saturated.

Referring to FIGURE 1, there is illustrated a saturable magnetic elementwith associated drive and output windings. Two drive windings 12 and 14are shown wound about the periphery of element 16. However, it is onlynecessary that there be one such drive winding, two being used where acoincident current application is desired. For this reason drive winding14 which is of like turns array and like turns number to winding 12, hasbeen shown dotted and will be discussed hereinafter in connection withcoincident current operation. Winding 12 is a continuous distributedwinding divided into two portions 18 and 2t by the relative windingdirections thereof. Portion 18 is wound oppositely to portion 29 andtherefore the field produced by current flowing in winding portion 18 isoppositely directed to that produced by current flow in portion 21Output winding 16 is wound about element 10 in a side-by-side relationto Winding portion 18. Winding portion 18 has fewer turns than portion2t} and preferably the total effective turns ratio of winding 18 towinding portion 20 is approximately 3:11. With this arrangement, it isseen that output winding 16 is more closely coupled, in the absence ofelement It) participation, i.e., in the absence of coupling from elementlit, to the smaller winding portion 18, than to the larger windingportion 20.

The hysteresis characteristics of element 10 is shown in FIGURE 1A. Thesolid line represents the curve obtained when a high frequency signal isapplied thereto, while the dotted line represents the curve when a lowfrequency drive signal is used.

To understand the operation of the circuit of FIGURE I assume themagnetization of element 10 has been biased to point 22 of FIGURE 1A bysome biasing means not shown. The biasing means may, for example, be acurrent carrying winding inductively coupled to element 10 and activatedby a suitable current source. When an input current pulse ofinsufficient magnitude to cause the magnetization of element 10 tobecome unsaturated is received on drive line 12, the magnetizationthereof moves to some point, for example, point 24, which is still inthe saturation region. As before mentioned, in the past the coupling ofinput or drive windings to output windings has given rise to undesiredoutputs with saturation conditions in the element because of residualpermeability in the core and air coupling, i.e., the coupling betweenthe drive and output windings even when the core is saturated issufficient to cause an undesired output signal to be induced in theoutput winding. This coupling effect is overcome by the windingarrangement of FIGURE 1. As above described, the output winding 16 ismore closely coupled to the portion of drive winding 12 of lesser numberof turns, i.e., portion 18, than to the oppositely wound portion ofgreater number of turns, i.e., portion 20. Thus the coupling is greaterbetween the output winding 16 and drive winding portion 18, than betweenoutput winding 16 and drive winding portion 20. Therefore, when acurrent pulse of insufiicient magnitude to drive the element out ofsaturation is applied on drive line 12, the field thereby produced fromdrive winding portion 18 is coupled to output winding 16 in a directionopposite to, and to a greater extent than is the field produced by thecurrent pulse from drive winding portion 20. However even though windingportion 20 has a greater number of turns than winding portion 13, with aproper choice of turns ratio, the net effect relative to output winding16 is a cancellation of fields and therefore negligible signal isinduced in output winding 16. Thus when the element is operating'in asaturated region, an insignificant output results for any inputinsufficient to cause operation in the saturated region.

Next, consider the case when the element 10 is operated in itsunsaturated region. Again assume that magnetization thereof is biased bymeans not shown into the saturation region to point 22, for example.When an input current pulse of sufficient strength to move themagnetization out of saturation, to point 26 for example, is applied todrive Winding 12, the corresponding flux change of element 10 causes asubstantial output signal to be induced in output winding 16. In thiscase since the element is operating in its high incremental permeabilityregion, a high percentage of the flux change produced i due to currentflowing in winding portion 20 is coupled 3 Hence a large signal isinduced in output winding 16. By properly choosing the number of turnsin winding portions 18 and 25], as will now be understood from theforegoing, a maximum ratio of unsaturated output operation to saturatedoutput operation may be obtained.

One important use of the above invention is in a magnetic core orelement memory matrix which uses coincident currents as means foraltering the states of these elements, although limitation to this useis not intended. In such matrices, predetermined elements are selectedfor writing infiorniation thereinto or reading information therefrom byactivating drive lines inductively coupled thereto with drive pulseseach of insuificient magnitude to cause these elements to change state.However, the total field produced by the coincidence of these pulses issufiicient to cause the element or elements receiving this total fieldto change states, the magnetization thereof moving through theunsaturated portion of its hysteresis curve thereby inducing asubstantial signal in an output winding coupled thereto. The elementsthat receive only a part of the total field have their magnetizationmoved only a portion of the way, along the hysteresis loop. This causesa signal, called a noise signal, to be induced in the output winding orwindings thereto coupled. The practical size arrays, e.g., 32 x 32 x 32elements, noise signals become quite important. The present invention asemployed in such a matrix will considerably reduce these noise signals,an output signal being produced only when the elements thereof areoperated in their unsaturated regions.

Referring again to FIGURE 1, the additional drive winding 14 is woundabout the periphery of element 1% in coincidence with and sidc-by-sidethe drive winding 12. Winding portions 23 and 30 of winding 14 correspond respectively to winding portions 18 and 2d of winding 12 and inthe preferred winding arrangement winding portion 28 has the same numberof turns wound in the same direction as winding portion 18 while windingportion 30 has the same number of turns wound in the same direction aswinding portion 2.0.

Assume that a constant current is applied to a bias winding (not shown)which is inductively coupled to the element 10. This current produces afield which biases the magnetization thereof into saturation to point22, for example. Provision is made for applying equal drive currentpulses to windings 12 and 14 as is usual in some conventional coincidentcurrent memory systems, the pulses applied to each winding being termedhalf pulses. When these drive pulses are applied coincidently towindings 12 and 14, the total field caused thereby moves themagnetization out of the saturation region to a point such as point 26in FIGURE 1A, producing a large change of flux through the outputwinding 16 and generating thereon a large output signal. This is calledthe full drive output. Since element is operating in its highincremental permeability region, a high percentage of the flux changedue to the applied fields from winding portions 20 and 30 is coupled tothe output winding 16. Consequently the flux change due to the fieldsdirected oppositely thereto'from winding portions 18 and 28 only cancela portion of the flux change due to winding portions 20 and 30. Thus alarge output signal results.

However, when a half pulse is applied to only one of the drive windings,e.g., winding 12, the magnetization thereof is not moved out ofsaturation, but instead moves to some point 24 where the incrementalpermeability is low. Since output winding 16 is more closely coupled towinding portions 18 and 28 respectively having less turns than windingportions 29 and St the coupling therebetween is greater than thecoupling between output winding 16 and winding portions 24 and 30. Byproperly selecting the ratio of turns respectively between windingportions 18 and 20 of winding 12, and winding portions 28 and 30 ofwinding 14, the fields caused by the half pulse flowing in either of thedrive windings are canceled relative to output winding 16 andsubstantially no noise signal results. The illustrated turns ratio of3:11 is exemplary or" an operable embodiment. Thus substantially nosignal is produced on output winding 16 when only one drive line isactivated with a half pulse, while a large signal is produced on outputwinding 16 when both drive lines are activated with half pulses and theratio of full drive output to half drive output is increased over thatobtainable with conventional winding distributions. Although only twodrive windings have been employed in the above described coincidentcurrent use, it is clear that three or more drive windings may be usedwithout departing from the scope of this invention. Therefore limitationto a two drive line employment is not intended.

Thus, it is apparent that there is provided by this invention a devicein which the various objects and advantages herein set forth aresuccessfully achieved.

Modifications of this invention not described herein will becomeapparent to those of ordinary skill in the art upon reading thisdisclosure. Therefore, it is intended that the material contained in theforegoing description and the accompanying drawings be interpreted asillustrative and not limitative, the scope of the invention beingdefined in the appended claims.

What is claimed is:

1. A method of using a device comprising a saturable magnetic element, adrive winding positioned for inductive coupling to said element, anoutput winding positioned for inductive coupling to said element, theoutput winding being positioned to be more closely inductive- 1y coupledirrespective of said element to a first portion of said drive windingthan to the remaining portion thereof, and the respective portions ofthe drive winding being oppositely poled, said method including the stepof magnetically saturating said element when a minimum output from saidoutput winding is desired and maintaining said element in an unsaturatedstate when a predetermined greater output is desired.

2. A method of using a device comprising a saturable magnetic element, afirst drive winding and a second drive winding positioned for inductivecoupling to said element, an output winding positioned for inductivecoupling to said element, the output winding being positioned to be moreclosely inductively coupled irrespective of said element to a firstportion of said drive windings than to the remaining portions thereof,and the respective portions of the drive windings being oppositelypoled, said method including the step of magnetically saturating saidelement by passage of current through both drive windings to so saturatethe element when a minimum output from said output winding is desired,and reducing the current in at least one of said drive windings formaintaining said element in an unsaturated state when a predeterminedgreater output is desired, the method being such that the device mayoperate as a coincident-current device.

3. A saturable magnetic core matrix switch the combination comprising: amagnetic core; an input winding magnetically linking said core andhaving oppositely wound first and second portions; an output winding anda bias winding magnetically linking said core; said input winding secondportion having substantially more turns than said first portion; saidoutput winding wound about said core so as to provide substantiallygreater air coupling with said input winding first portion than withsaid second portion; the arrangement being such that when the magneticstate of said core is driven into saturation by a bias signal coupled tosaid bias Winding the close coupling of the input Winding first portionand the remote coupling of the input winding second portion, both withrespect to the output winding, causes a cancellation of the inducednoise signal in the output winding, but when the magnetic state of saidcore is driven into an unsaturated condition 'by an input signal coupledto said input winding the greater number of turns of the input e)winding second portion, as compared to the lesser number of turns of thefirst portion, acting through the high incremental permeability of thecore causes an appreciable signal to be induced in said output winding.

4. A saturable magnetic core matrix switch, the combination comprising:a saturable magnetic core; an input winding magnetically linking saidcore and having oppositely wound first and second portions; an outputwinding and a bias winding magnetically linking said core; said inputWinding first portion having substantially less turns than said secondportion; said output winding wound about said core so as to providesubstantially greater air coupling with said input winding first portionthan with said second portion; the arrangement being such that when themagnetic state of the core is driven into saturation by a bias signalcoupled to said bias winding the close coupling of the input windingfirst portion and the remote coupling of the input winding secondportion, both with respect to the output winding, cause a cancellationof the induced noise signal in the output winding, which noise signal iscaused by both air coupling and core coupling of the input winding firstand second portions to the output winding, but when the magnetic stateof said core is driven out of said saturated condition by an inputsignal coupled to said input winding the greater number of turns of theinput winding second portion, as con1- pared to the lesser number ofturns of the first portion, acting through the high incrementalpermeability of the core causes an appreciable signal to be induced insaid output winding.

, winding portions, said first portion having substantially less turnsthan said second portion; said output winding inductively coupled tosaid first and second input windings so as to provide substantiallygreater air, coupling with said first portion than with said secondportion; a bias Winding inductively coupled to said core; bias signalmeans coupled to said bias winding for selectively placing the magneticstate of said core in a first substantially saturated condition;substantially similar first and second half-select signal meansselectively coupled to said first and second input windings,respectively; said first and second half-select signal meansindividually incapable of'driving the magnetic state of said core out ofsaid first substantially saturated condition, but, when coincident,collectively capable of driving the magnetic state of said core out ofsaid first substantially saturated condition into its condition of highincremental permeability; the arrangement being such that when themagnetic state of said core is placed in said first substantiallysaturated condition by said bias signal means the close coupling of saidfirst and second input windings first portions and the remote couplingof said first and second input windings second portions, both withrespect to the output winding, cause a cancellation of the induced noisein the output winding, which noise signal is caused by both air couplingand core coupling of the first and second input windings first andsecond portions to the output winding, when only said first half-selectsignal means is coupled to said first input winding drivingthe magneticstate of said core through the area of substantial saturation but notinto the condition of high incremental permeability, but when said firstand second half-select signal means are coincidentally coupled to saidfirst and second windings the magnetic state of said core is driven intoits condition of high incremental permeability causing an appreciablesignal to be induced in said output winding.

References tfliteil in the file of this patent UNITED STATES PATENTSJohannesen Mar. 26, 1912 Elmen Dec. 31, 1918 OTHER REFERENCES

5. A SATURABLE MAGNETIC CORE MATRIX SWITCH, THE COMBINATION COMPRISING:A MAGNETIC CORE; AN OUTPUT WINDING INDUCTIVELY COUPLED TO SAID CORE;FIRST AND SECOND SUBSTANTIALLY SIMILAR INPUT WINDINGS INDUCTIVELYCOUPLED TO SAID CORE WITH EACH INPUT WINDING HAVING FIRST AND SECONDWINDING PORTIONS, SAID FIRST PORTION HAVING SUBSTANTIALLY LESS TURNSTHAN SAID SECOND PORTION; SAID OUTPUT WINDING INDUCTIVELY COUPLED TOSAID FIRST AND SECOND INPUT WINDINGS SO AS TO PROVIDE SUBSTANTIALLYGREATER AIR COUPLING WITH SAID FIRST PORTION THAN WITH SAID SECONDPORTION; A BIAS WINDING INDUCTIVELY COUPLED TO SAID CORE; BIAS SIGNALMEANS COUPLED TO SAID BIAS WINDING FOR SELECTIVELY PLACING THE MAGNETICSTATE OF SAID CORE IN A FIRST SUBSTANTIALLY SATURATED CONDITION;SUBSTANTIALLY SIMILAR FIRST AND SECOND HALF-SELECT SIGNAL MEANSSELECTIVELY COUPLED TO SAID FIRST AND SECOND INPUT WINDINGS,RESPECTIVELY; SAID FIRST AND SECOND HALF-SELECT SIGNAL MEANSINDIVIDUALLY INCAPABLE OF DRIVING THE MAGNETIC STATE OF AID CORE OUT OFSAID FIRST SUBSTANTIALLY SATURATED CONDITION, BUT, WHEN COINCIDENT,COLLECTIVELY CAPABLE OF DRIVING THE MAGNETIC STATE OF SAID CORE OUT OFSAID FIRST SUBSTANTIALLY SATURATED CONDITION INTO ITS CONDITION OF HIGHINCREMENTAL PERMEABILITY; THE ARRANGEMENT BEING SUCH THAT WHEN THEMAGNETIC STATE OF SAID CORE IS PLACED IN SAID FIRST SUBSTANTIALLYSATURATED CONDITION BY SAID BIAS SIGNAL MEANS THE CLOSE COUPLING OF SAIDFIRST AND SECOND INPUT WINDINGS FIRST PORTIONS AND THE REMOTE COUPLINGOF SAID FIRST AND SECOND INPUT WINDINGS SECOND PORTIONS, BOTH WITHRESPECT TO THE OUTPUT WINDING, CAUSE A CANCELLATION OF THE INDUCED NOISEIN THE OUTPUT WINDING, WHICH NOISE SIGNAL IS CAUSED BY BOTH AIR COUPLINGAN CORE COUPLING OF THE FIRST AND SECOND INPUT WINDINGS FIRST AND SECONDPORTIONS TO THE OUTPUT WINDING, WHEN ONLY SAID FIRST HALF-SELECT SIGNALMEANS IS COUPLED TO SAID FIRST INPUT WINDING DRIVING THE MAGNETIC STATEOF SAID CORE THROUGH THE AREA OF SUBSTANTIAL SATURATION BUT NOT INTO THECONDITION OF HIGH INCREMENTAL PERMEABLILITY, BUT WHEN SAID FIRST ANDSECOND HALF-SELECT SIGNAL MEANS ARE COINCIDENTALLY COUPLED TO SAID FIRSTAND SECOND WINDINGS THE MAGNETIC STATE OF SAID CORE IS DRIVEN INTO ITSCONDITION OF HIGH INCREMENTAL PERMEABILITY CAUSING AN APPRECIABLE SIGNALTO BE INDUCED IN SAID OUTPUT WINDING.